School holiday dates vary from one Education Authority to another. A comprehensive list of all UK school holidays is provided on the 'half term dates' website.
The tourist offices for Dieppe, Rouen and Neufchatel provide a wealth of useful information about the area. You could also take a look at the Seine-Maritime tourist office website.
There are websites for the Chateau de Mesnières, the Bois des Moutières in Varengeville-sur-Mer and the Chateau de Miromesnil. If you are visiting Varengeville you might consider taking lunch or dinner at La Terrasse. You could also visit the Church of St Valery where George Braque is buried.